The present invention relates generally to a method and corresponding apparatus for viewing images. More specifically, the present invention relates to a method and corresponding apparatus for viewing full-surround, e.g., spherical, image data.
Systems and techniques for changing the perspective of a visible image in producing a resultant image, or systems and methods of transforming an image from one perspective form to another have been the subject of scientific thought and research for many years. Systems and techniques for transforming visible images can generally be divided into three separate categories:                (1) perspective generation systems and methods suitable for applications such as flight simulators;        (2) three-dimensional (3D) to two-dimensional (2D) conversion systems and methods; and        (3) miscellaneous systems and methods.        
The first category includes U.S. Pat. No. 3,725,563, which discloses a method of and apparatus for raster scan transformations using rectangular coordinates which are suitable for electronically generating images for flight simulators and the like. More specifically, the patent discloses a technique for raster shaping, whereby an image containing information from one viewpoint is transformed to a simulated image from another viewpoint. On the other hand, U.S. Pat. No. 4,763,280 discloses a curvilinear dynamic image generation system for projecting rectangular coordinate images onto a spherical display surface. In the disclosed system, rectangular coordinates are converted to spherical coordinates and then the spherical coordinates are distorted for accomplishing the desired simulation of curvature.
The second category of systems and techniques perform 3D-to-2D conversion, or vice versa. For example, U.S. Pat. No. 4,821,209 discloses a method of and apparatus for data transformation and clipping in a graphic display system, wherein data transformation is accomplished by matrix multiplication. On the other hand, U.S. Pat. No. 4,667,236 discloses a television perspective effects system for providing perspective projection whereby each point of a three-dimensional object is projected onto a two-dimensional plane. New coordinates X′ and Y′ are prepared from the original coordinates X, Y and Z, and the viewing distance D, using the general formulas X′=XD/Z and Y′=YD/Z. As the object to be displayed is rotated around the X or Y axis, the viewing distance D is changed for each point.
In the third category, miscellaneous systems and methods are disclosed by, for example, U.S. Pat. No. 5,027,287, which describes a device for the digital processing of images to obtain special geometrical effects wherein digital image data corresponding to intersection points on a rectangular X,Y grid are transposed by interpolation with respect to intersection points of a curved surface. U.S. Pat. No. 4,882,679, on the other hand, discloses a system and associated method of reformatting images for three-dimensional display. The disclosed system is particularly useful for generating three-dimensional images from data generated by diagnostic equipment, such as magnetic resonance imaging.
However, none of the above described methods or systems permit viewing in circular perspective, which is the best way to view spherical data. Circular perspective does all that linear perspective does when zoomed in, but it allows the view to zoom out to the point where the viewer can see almost everything in the spherical data simultaneously in a visually palatable and coherent way.
What is needed is a method for viewing full-surround, e.g., spherical, image data employing circular perspective. Moreover, what is needed is an apparatus for viewing full-surround, e.g., spherical, image data employing circular perspective. What is also needed is a method for viewing full-surround, e.g., spherical, image data employing circular perspective which is computationally simple. Preferably, the method for viewing full-surround, e.g., spherical, image data employing circular perspective can be employed on any personal computer (PC) system possessing a three dimensional (3-D) graphics capability.